The present invention relates generally to digital computer network technology and more specifically to methods and apparatus for implementing improved sign-on procedures for nodes desiring to access the Head End of an access network.
Broadband access technologies such as cable, fiber optic, and wireless have made rapid progress in recent years. Recently there has been a convergence of voice and data networks which is due in part to US deregulation of the telecommunications industry. In order to stay competitive, companies offering broadband access technologies need to support voice, video, and other high-bandwidth applications over their local access networks. For networks that use a shared access medium to communicate between subscribers and the service provider (e.g., cable networks, wireless networks, etc.), providing reliable high-quality voice/video communication over such networks is not an easy task.
One type of broadband access technology relates to digital video broadcasting (DVB) networks. An example of a conventional DVB network is shown in FIG. 1 of the drawings. As shown in FIG. 1, the DVB network 100 includes a Head End 102 which is configured to provide interactive services and communications with a plurality of network nodes or user terminals 120. In order to provide interactive network functionality, the Head End typically includes an interactive network adapter (INA) 106, whose functions are similar to the functions of a cable modem termination system (CMTS), which is located at the Head End of a cable network.
In order for data to be able to be transmitted effectively over a wide area network such as a DVB network or other broadband computer network, a common standard for data transmission is typically adopted by network providers. A commonly used and well known standard for implementing digital video broadcasting and interaction channels is the ETSI standard for Digital Video Broadcasting and DVB Interaction Channels For Cable Television Distribution Systems (herein referred to as the “ETSI standard”). The ETSI standard has been publicly presented by the European Broadcasting Union in a document entitled “ETSI ES 200 800 V1.2.1”, on April, 2000. That document is incorporated herein by reference in its entirety for all purposes, and may be accessed via the worldwide web at www.etsi.org.
As shown in FIG. 1, the interactive network adapter 106 communicates with the plurality of user terminals 120 via at least one downstream interaction channel 117, and at least one upstream interaction channel 119. A plurality of different hardware and software components forming interaction network 107 provides the necessary infrastructure for enabling communication between the interactive network adapter (INA) 106 and the plurality of user terminals 120. The interactive network adapter 106 may also be used to communicate with an interactive service provider 112.
The downstream interaction channel(s) 117 provide a forward interaction path from a service provider to the user. These channels may be used to provide information by the service provider to the user, along with other required communications for the interactive service provision. In an alternate embodiment (not shown) the downstream interaction channels 117 may be embedded into the broadcast channels 115.
One or more upstream interaction channel(s) 119 provide a return interaction path from the user to the service provider. The upstream channels may be used to make requests to the service provider or to answer questions. Typically each upstream channel is configured as a narrow band channel, and is commonly referred to as a “return channel”.
In the example of FIG. 1, the service provider may be considered to be the entity which controls portion 150 of the DVB network and provides interactive broadband access to the plurality of users. For example, the service provider which manages network portion 150 may correspond to a cable operator facility, and the network 150 may correspond to a cable network. The components of the interactive sub-system (e.g., 112, 106, 107, 117, 119, 124) of the DVB cable network 150 operate in a way that is comparable with the well-known DOCSIS protocol. The DOCSIS standard has been publicly presented by Cable Television Laboratories Inc. (Louisville, Colo.) in a document entitled, DOCSIS 1.1 RF Interface Specification (document control number SP-RFIv1.1-106-001215, Dec. 15, 2000). That document is incorporated herein by reference in its entirety for all purposes.
As show in FIG. 1, the Head End 102 may also include a broadcast network adapter 104 which forms part of a broadcast delivery system or channel for providing content to end users. The broadcast network adapter 104 may communicate with the plurality of user terminals 120 via one or more downstream broadcast channels 115. Typically, the downstream broadcast channels 115 are configured as unidirectional broadband broadcast channels suitable for carrying video, audio, and/or data signals from a broadcast content provider 110. According to a specific embodiment of the present invention, the components of the broadcast sub-system (e.g., 110, 104, 105, 115, 122) may correspond to a conventional one-way television broadcast network.
As shown in FIG. 1, each user terminal (e.g. 120a) comprises a network interface unit (NIU) 125 and a set top unit 126. The functions performed by the network interface unit 125 are similar to the functions performed by a cable modem residing in a DOCSIS cable modem network. In the example of FIG. 1, the user terminal 120a is configured to provide an interface for both broadcast and interaction channels. Accordingly, the network interface unit (NIU) may include a broadcast interface module 122 and an interactive interface module 124. In a specific implementation where the user terminal 120a is configured as an interactive set-top box, the interaction channels 117, 119 may be used for interactive TV programs. In a specific embodiment where the user terminal 120a is configured as a cable modem, the interactive portion of the DVB network 100 may correspond to an interactive cable network. In this latter embodiment, content from the broadcast content providers may be provided to the cable modems via the downstream interaction channels, and the broadcast channel 115 as well as other components of the broadcast subsystem may be omitted.
According to the ETSI standard, the interactive system 100 of FIG. 1 includes at least one forward interaction path (117) and at least one return interaction path (119). The general concept is to use downstream transmission from the INA 106 to the NIUs 125 to provide synchronization and information to all NIUs. This allows the NIUs to adapt to the network and send synchronized information upstream.
Upstream transmissions from the NIUs to the Head End are divided into multiple timeslots using the technique known as Time Division Multiple Access (TDMA). Each of these timeslots may be allocated for use by different network users. A counter at the INA is sent periodically to the NIUs, so that all NIUs work with the same clock. This gives the opportunity to the INA to assign timeslots to different users.
Typically, three types of access modes are used to allow NIUs to communicate with the INA. The first access mode is based on contention access, which lets users send information upstream during designated contention-based timeslots. During these contention-based timeslots, there is a risk that one or more collisions may occur with other users' transmissions. NIU sign-on operations are performed using contention-based timeslots (commonly referred to as Ranging slots). The second and third modes of access are non-contention based, where the INA either provides a finite amount of slots to a specific NIU, or provides a given bit rate requested by a NIU until the INA stops the connection. These access modes are dynamically shared among timeslots, which allows NIUs to know when contention based transmission is or is not allowed. This helps to avoid collisions for the two non-contention based access modes.
As part of the sign-on procedure described in the ETSI standard, the INA periodically sends Sign-On Request messages downstream to the NIUs. Any NIUs which wants to sign-on may reply to the Sign-On Request message by sending a Sign-On Response message upstream to the INA. However, since the Ranging timeslots allocated to the NIUs (for transmitting their Sign-On Response messages) are contention based, collisions will occur if more than one NIU transmits a Sign-On Response message during the same Ranging timeslot. Typically, when a collision occurs, the INA is unable to identify or decipher any of the Sign-On Response messages which were transmitted by the NIUs, and therefore will be unable to respond to any of the NIUs which sent the Sign-On Response messages.
When Sign-On Response message collisions occur, the corresponding NIUs are required to wait a randomized time interval before attempting to transmit another Sign-On Response message to the INA, thereby further delaying the sign-on process. Moreover, such delays increase as the number of NIUs attempting to sign-on to the DVB network increase. Thus, for example, if a network failure were to occur, the end users may experience significant disruptions in service as a result of the delays associated with the conventional NIU sign-on process.
Accordingly, it will be appreciated that there exists a continual need to improve access network protocols in order to better utilize network resources and minimize service disruptions and delays.